Among sexually reproducing organisms, the allocation of maleness and femaleness to offspring occurs in many ways, most familiarly, via sex chromosomes (XX females and XY males in humans, flies; ZW females and ZZ males in birds, butterflies). Although closely-related species often differ in their sex determination mechanisms, why those evolve is poorly understood. The marine crustacean Tigriopus californicus has many genetically isolated populations and polygenic (genetic, but non-chromosomal) sex determination. Previous work with a laboratory-created hybrid population revealed that females, but not males, are often heterozygous across an entire chromosome (bearing one copy from each original population), suggesting that it could be acting as a Z/W sex chromosome. This project will use next-generation DNA sequencing on individuals from this hybrid population and its wild progenitors to identify identify the sex determination mechanism in each population and to ascertain whether the hybrid population has evolved a novel sex chromosome.
This project investigates the genetic basis of sex determination in copepods, one of the most abundant animal groups on the planet. Sex chromosomes are a predictable outcome of evolution. The emergence of a sex chromosome in a hybrid population would suggest that sex determination mechanism switches could be a consequence of hybridization-induced genomic disruption. This is especially important in light of the increasing hybridization occurring in natural populations due to human-driven processes, such as species introductions and climate change-induced range shifts. In addition, the project will include extensive mentoring of undergraduates, and an evolution and science communication workshop at the Aquarium of the Pacific, Long Beach, CA
